Help for logic

Question

Hi
I have one scenerio. I need to create a table wtih ID,creation_dt,password. I have to maintain password history.
If I first time login and enter a new pwd then it will store in my table. next time he/she change the password then it will also store in my table. upto 5 times. In the mean time If I give new passwords..it has to check with old passwords. if it same then display error message. If sixtime enter with new password then first one (old) password will be erase from the table.
For this scenerio....What kind of table (normal table / object type / varray/nested) I have to create? how to store the data? how to delete first row when I insert 6th time with new password?
Please help me in this regard...?
For example..
ID create_dt password
1 01/01/2008 abc
2 10/10/2010 xyz
1 12/03/2009 pqr
3 24/12/2008 abcd
1 01/10/2010 wxyz
2 22/12/2011 hijk
1 19/09/2011 rstu
2 10/01/2011 abc12
1 11/12/2011 defg
4 01/01/2008 klmn
Now if id 1 enter update the password then his first record(old one) can be erased. 01/01/2008 abc.
I need to implement this requirement .. Please your help / advises are very important.
Help me..!!
Regards
SA

Answer 1

can you manage you inserts into the password history table through a procedure?
/* Formatted on 6/14/2011 4:11:33 PM (QP5 v5.149.1003.31008) */
CREATE TABLE password_history
   user_id     INTEGER,
   create_dt   DATE,
   password    VARCHAR2 (20),
   CONSTRAINT password_history_uq UNIQUE (user_id, password)
CREATE OR REPLACE PROCEDURE password_history_mgr (
   p_user_id     password_history.user_id%TYPE,
   v_password    password_history.password%TYPE)
IS
BEGIN
   FOR c IN (SELECT user_id,
                    create_dt,
                    password,
                    ROW_NUMBER () OVER (ORDER BY create_dt) rn
               FROM password_history
              WHERE user_id = p_user_id)
   LOOP
      IF c.rn > 6
      THEN
         DELETE FROM password_history
               WHERE     user_id = c.user_id
                     AND create_dt = c.create_dt
                     AND password = c.password;
      END IF;
   END LOOP;
   INSERT INTO password_history
        VALUES (p_user_id, SYSDATE, v_password);
END;
exec password_history_mgr(1,'ghi');